An inkjet printer is a printing machine which prints by ejecting ink onto a sheet, and has an ink head from which ink is ejected and an ink cartridge. The ink cartridge is mounted to an upper part of the print head to store an ink supply to the print head. There is an ink cartridge which has: an ink tank provided with an ink absorber made of a porous material to hold ink; and an ink supply tube through which ink is supplied from the ink tank to the print head. The ink supply tube is attached to the ink tank with an end reaching inside the tank.
The conventional structure has defective print problems caused by bubbles which enter a passage connecting the place where the tube is attached to the print head, that is, inside the ink supply tube, in attaching the tube.
The problems are addressed in, for example, Japanese published unexamined patent application 5-131645 (Tokukaihei 5-131645/1993; published on May 28, 1993). The disclosure shows a print head having a filter tank where ink experiences turbulent flows and slipstream to destroy bubbles in it and goes through a filter before being fed to the print head.
Another example is Japanese published unexamined patent application 2002-36557 (Tokukai 2002-36557; published on Feb. 5, 2002). The disclosure shows a cartridge capable of preventing bubbles from interrupting ink supply by rendering the buoyancy of the bubbles inside the ink supply chamber greater than the drag force caused by high ink velocity so as to prevent bubbles from growing in an ink supply chamber.
However, the approach disclosed in the patent application 5-131645 still has defective print problems: bubbles may attach to and clog the filter, thereby obstructing ink flow. Bubbles can enter the ink head unless the mesh of the filter is substantially small.
The approach taken in the patent application 2002-36557 has defective print problems too. The approach is not able to remove bubbles from inside the ink supply tube once they are trapped in it.